Immersion sublances and immersion probes are broadly used in converter furnaces during steelmaking processes. Typically, pig iron and scrap metal are discharged into the converter furnace, which fuses them together at a high temperature (e.g., 1600 to 1750° C.), thus producing steel.
In order to produce a high quality product having ideal chemical characteristics, the molten metal has to be subjected to several chemical analyses. The aim is to monitor all the chemical elements contained in the steel, for example, by controlling, among others, the carbon, carbon equivalents and silicon concentration, or by monitoring the hardness, resistance, machinabily, temperature, and/or oxidation level.
Such chemical analyses are performed by means of sensing or sampling the molten metal, those operations being performed by sensors located at the end of an immersion probe.
Conventionally, during the production of molten metal, a blowing lance is used to blow oxygen inside the converter furnace at supersonic speed onto molten slag and molten metal.
In parallel, the assembly of an immersion sublance and an immersion probe is inserted from the external environment into the inside of the converter furnace following a longitudinal direction, such that only the immersion probe of said assembly is submerged into molten slag and subsequently into molten metal. Once in contact with molten metal, the immersion probe is able to perform measurements and/or take samples of molten metal by means of sensors or sampling chambers. Upon fulfillment of those tasks, the assembly of the immersion sublance and the immersion probe is taken out of the converter furnace, and the immersion probe is then disconnected from the immersion sublance and then discarded.
The connection of the immersion probe to the immersion sublance is performed before the insertion of the assembly into the converter furnace, said connection being partially automated.
As previously mentioned, the immersion probe is used only once during the immersion and/or measurement process. On the other hand, the immersion sublance can be reused, for it is provided with a longer service life.
Considering that the immersion sublance is used for several immersions and/or measurements, deformations due to harsh ambient conditions and high temperatures inside the converter furnace have been observed after several immersions and/or measurements by the sublance. Such deficiencies are quite common and severe, resulting in difficulty connecting a new immersion probe to the immersion sublance.
More specifically, a deformed immersion sublance can present connection problems with a new immersion probe, resulting in clearance problems between the sublance holder and the immersion probe. Such characteristics are not desirable, and can lead to various problems.
Since the immersion probe structure is typically made of cardboard and does not possess precise dimensions, it has been observed that the immersion probe cannot completely cover the immersion sublance holder. Furthermore, depending on the climatic conditions, as well as the storage location of the immersion probes, it is known that deformations can occur on the cardboard constituting the probes' casings, creating radial or longitudinal variations. Considering this problem, it is known that when the assembly of an immersion sublance and an immersion probe is inserted into the converter furnace, some molten metal splashes might land on the sublance holder, making the connection to a new immersion probe difficult.
In order to avoid this problem, an attempt has been made in the art to counter the deformation of the immersion sublance. The European Patent EP-A1-69433 describes a sublance presenting a fixed upper end and a lower end which can rotate. It specifically discloses that the lower portion of the immersion sublance gets deformed after the first immersion in molten metal, then the sublance is taken out of the converter furnace and its lower end is rotated 180°. After said rotation, the sublance is then immersed anew. According to the teachings of European Patent EP-A1-69433, this feature allows the lower portion to come back to its original position (before the first immersion).
Another known solution is described by the U.S. Pat. No. 4,566,343. This patent discloses an immersion sensor comprising a rubber seal designed to prevent molten metal from penetrating into the immersion sublance.
In addition, another solution aimed at improving the connection between the immersion probe and the sublance holder is also known in the art. US-B2-7370544 describes the use of a spring or an elastic ring on the sublance holder. This solution is problematic, considering that the immersion sublances currently commercialized require some adjustments in order to accommodate the spring or the elastic ring. In this way, it becomes mandatory to stop the measurement process in order to adapt the sublance described in US-B2-7370544.
Considering the above solutions, it is observed that in the state of the art, the use of an immersion probe with a variable connection length, able to compensate for length variations in the longitudinal and/or radial directions of the immersion sublances, is not known.
Furthermore, the current state of the art provides no solution for the use of an immersion probe with a variable connection length without requiring the adaptation of the immersion sublances, such that immersion sublances currently commercialized could be used without requiring any adaptation.